1. Technical Field
The present invention relates to a scanning unit of a position measuring arrangement for scanning the measuring graduation of a scale, having at least one heat-generating electrical component in an interior space of the scanning unit, a base body, which can be installed, fixed in place, on an object to be measured, wherein the base body comes into contact with a first contact face at a first location of the object to be measured, and having a contact element with a second contact face which, in the course of installing the base body, comes into contact at a second location of the object to be measured, and with a heat-conducting path, which is designed for transferring heat generated by the electrical component from the interior space of the scanning unit to the contact element.
2. Background Information
Position measuring arrangements, such as are described in U.S. Patent Application Publication No. 2004/0263846, the entire contents of which are incorporated herein by reference, for example, are used for measuring lengths, as well as paths, and are employed in particular in connection with processing machinery for measuring the relative movement of a tool with respect to a workpiece to be processed, and also increasingly in the semiconductor industry for positioning wafers.
The demands made on position measuring arrangements continue to increase, higher resolution, as well as greater accuracy and reproducibility of the position measuring arrangement, are continuously demanded. At the same time it is desired that a compact design, as well as a simple and interference-proof measured value generation, are provided.
A compact design and an interference-proof measured value generation and measured value transmission require the integration of increasingly more electrical components in the scanning unit itself. Sensor chips are therefore increasingly employed, in which an array of scanning sensors can be arranged in the smallest space, for example photo-sensitive detectors, in case of a scale which can be scanned photo-electrically, as well as signal processors such as, for example, A/D converters, amplifiers, micro-processors and interfaces. In addition, the measuring graduation to be scanned by the scanning unit becomes increasingly finer, and the displacement speed of the scanning unit in relation to the scale becomes increasingly higher, which leads to a considerable increase in the frequency of the scanning signals which must be processed by the signal processors. The amplifiers required for this processing generate relatively much heat. An increased heat generation in the scanning unit results from this. On the one hand, this heat affects the electrical components themselves in a negative manner in that their service life is reduced and characteristic data change over time. On the other hand, the heat also negatively affects the mechanical portion of the scanning component in that components of the scanning unit expand in an undefined manner, which can lead to measurement inaccuracies.